Note: This review covers salicin-containing species of Salix, which includes Salix alba, Salix fragilis, Salix purpurea, and Salix pentandra. Additionally, salicin and salicylates are present not only in willow, but also other Salicaceae family plants such as poplar (several different Populus genus members), as well as completely different plant family members, such as birch (Betula spp; Betulaceae family), and meadowsweet (Filipendula ulmaria; Rosaceae family). These compounds are not specific to just willow. Although salicylates are discussed in this monograph they are not the focus of this monograph.

In the United States, willow bark is used by herbalists as a fever reducer, a mild pain reliever, and an anti-inflammatory. There is evidence that supports willow bark use for osteoarthritis and lower back pain. Early study suggests that willow bark extracts may not be helpful for rheumatoid arthritis, but further study is needed to form strong conclusions. Taking willow bark may increase the risk of bleeding; however, this risk may be less than taking aspirin.

Several countries in Europe have approved willow bark for pain and inflammatory disorders. The German Commission E has approved willow bark for fever, rheumatic ailments, and headaches. The British Herbal Compendium indicates that willow bark can be used for rheumatic and arthritic conditions, and fever associated with cold and influenza. In France, willow bark has been approved as a pain reliever to treat headache and toothache pain, as well as painful articular (joint) conditions, tendonitis, and sprains. The European Scientific Cooperative on Phytotherapy (ESCOP) has approved willow bark extract for the treatment of fever, pain, and mild rheumatic complaints.

Willow bark contains salicylates that may present a safety risk to people, specifically those with aspirin allergy or sensitivity, those using blood thinners, and children with flu-like symptoms due to Reye's syndrome.

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

GRADE *

Willow bark has been studied for its effects in the treatment of lower back pain. Studies have found willow bark to be as effective to other methods. Cost effectiveness studies have also found that willow bark was cost effective. Due to the small number of studies available, further research is needed to confirm willow bark's efficacy for lower back pain.

B

Willow bark has been used to treat many types of inflammatory conditions, including headache. One study investigated a salicin topical cream for the treatment and/or prevention of migraine and tension-type headache. Although early study is promising, additional study is needed to form any firm conclusions.

C

Willow bark is a traditional pain relieving agent for osteoarthritis. Several studies have found mixed results. Additional research is needed in this area before any firm conclusions can be made.

C

Based on limited available evidence, willow bark extract lacks an effect in the treatment of rheumatoid arthritis (RA). Additional study is needed to make a firm conclusion.

C

Use of a combination product containing will bark resulted in increased weight loss over placebo. However, more clinical research is needed before any firm conclusions can be made.

C

* Key to grades

A: Strong scientific evidence for this useB: Good scientific evidence for this useC: Unclear scientific evidence for this useD: Fair scientific evidence for this use (it may not work)F: Strong scientific evidence against this use (it likley does not work)

Tradition / Theory
The below uses are based on tradition, scientific theories, or limited research. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. There may be other proposed uses that are not listed below.

According to secondary sources, the German Commission E recommends doses of willow bark extract of 60-120 milligrams of total salicin (active ingredient) daily.

For lower back pain, 120-240 milligrams of willow bark extract have been taken by mouth daily for four weeks. In addition, 1,573-1,600 milligrams of willow bark have been taken by mouth daily for 2-6 weeks.

For osteoarthritis, 1,360-2,160 milligrams of willow bark extract containing 240 milligrams of salicin have been taken by mouth daily for up to six weeks. Additionally, a willow bark extract containing 120 milligrams of salicin has been taken by mouth twice daily for six weeks. Coated tablets containing 1,360-2,160 milligrams of willow bark extract have been taken by mouth daily for two weeks.

For rheumatoid arthritis, willow bark extract containing 120 milligrams of salicin has been taken twice daily for six weeks.

Children (younger than 18 years)

There is no proven safe or effective dose for willow bark in children.

Safety
The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.

Allergies

Avoid with known allergy or sensitivity to aspirin, willow bark (Salix species.), or any of its parts, including salicylates.

Side Effects and Warnings

Willow bark is likely safe when used under the supervision of a health care professional and in doses of 120-240 milligrams of salicin for up to six weeks.

Willow bark may alter blood pressure. Caution is advised in people taking drugs or herbs and supplements that affect blood pressure.

Willow bark may increase the risk of bleeding. Caution is advised in people with bleeding disorders or taking drugs that may increase the risk of bleeding. Dosing adjustments may be necessary.

Willow bark may increase the risk of bleeding when taken with drugs that increase the risk of bleeding. Some examples include aspirin, anticoagulants ("blood thinners") such as warfarin (Coumadin®) or heparin, anti-platelet drugs such as clopidogrel (Plavix®), and non-steroidal anti-inflammatory drugs such as ibuprofen (Motrin®, Advil®) or naproxen (Naprosyn®, Aleve®).

Willow bark may lower blood sugar levels. Caution is advised when using medications that may also lower blood sugar. People taking drugs for diabetes by mouth or insulin should be monitored closely by a qualified healthcare professional, including a pharmacist. Medication adjustments may be necessary.

Willow bark may increase the amount of drowsiness caused by some drugs. Examples include benzodiazepines such as lorazepam (Ativan®) or diazepam (Valium®), barbiturates such as phenobarbital, narcotics such as codeine, some antidepressants, and alcohol. Caution is advised while driving or operating machinery.

Willow bark may increase the risk of bleeding when taken with drugs that increase the risk of bleeding. Some examples include aspirin, anticoagulants ("blood thinners") such as warfarin (Coumadin®) or heparin, anti-platelet drugs such as clopidogrel (Plavix®), and non-steroidal anti-inflammatory drugs such as ibuprofen (Motrin®, Advil®) or naproxen (Naprosyn®, Aleve®).

Hyson MI. Anticephalgic photoprotective premedicated mask. A report of a successful double-blind placebo-controlled study of a new treatment for headaches with associated frontalis pain and photophobia. Headache 1998;38:475-477.

The information in this monograph is intended for informational purposes only, and is meant to help users better understand health concerns. Information is based on review of scientific research data, historical practice patterns, and clinical experience. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions.